This thesis concerns the development of a measurement method for determination in the field of the thermal conductivity of the insulation in buried district heating mains.

The thermal conductivity of the insulation is calculated from the measured value of the radial heat flow through the heating main, the measured temperature difference across the insulation, and the dimensions of the heating main. The heat flow has been measured with a heat flux sensor which was fitted to the surface of the casing. The temperature has been measured with copper/constantan thermocouples.

It is a necessary condition for the method used in the project for determination of the thermal conductivity of the heating main insulation that the heating main is uncovered and is not in contact with the surrounding soil over a distance of about 1.5 m and that the measurements are made directly on the heating main. In this way, no account need be taken of the material surrounding the heating main, nor of the effect of this material on the measurements. No interference is needed with the heating main which would affect the distribution of the district heating water, and the heating main can remain in operation during measurements.

Shielding insulation consisting of preformed insulation sections which were placed over the casing of the heating main and covered the heat flux sensor and some of the casing. The function of this insulation was to shield the heat flux sensor from external thermal disturbances. In the field measurements, a copper guard plate of 0.5 mm thickness, the temperature of which could be adjusted, was also placed over the shielding insulation in order to maintain the temperature on the heat flux sensor as constant as possible.

When temperature and heat flow are measured, the instruments used will be affected by conditions which prevail at the time of measurement. It is therefore very important to analyse the sources of error which may arise in the measuring situation at hand.

The effect of these factors on the measured values has been studied by

' laboratory measurements

' theoretical calculations

' field measurements

On the basis of the resulting values of heat flows and temperatures obtained in field measurements on plastic heating mains which were operating under normal conditions, the thermal conductivity of the insulation of the main has been estimated.

The method has been tested on plastic heating mains with directly foamed insulation, since this is the most common type of heating main both in the existing district heating network and in new construction. The measuring method can also be used on other circular heating mains.

This study focuses on the necessity of having knowledge about different energy saving measures when renovations and reconstructions are planned and designed. It is also of great importance to have routines to follow up what effects the actions taken have had on the energy consumption as well as on the indoor climate when the renovation is completed. A big part of the existing buildings in Sweden are built during a ten-year period between 1965 and 1974. When these buildings are to be renovated there is a great potential for energy saving.

In the IEA Network Supervision project a special method, the Tx-factor method, is investigated. Several other methods exist for in-situ heat loss determination from district heating (DH) pipes. These methods have advantages and disadvantages compared to the Tx-factor method. It is the purpose of this work to make a comparison of the methods on a particular DH pipe. This makes this investigation special as in most previous work only one or very few methods have been applied on the same DH pipe. The purpose of this work was thus to go out to the site and make measurements of the heat loss from the DH pipe at this particular time of the year - an estimate of annual heat losses could then to be made afterwards. The aim of this work being to develop methods for practical applications not very sophisticated tools were used at the experimental site. This means that although very advanced equipment could have been used for determining the centre line and the depth of the DH pipe only measurement sticks, water levels and strings were used. For the same reasons the temperature sensors were installed by using measurement sticks

This report presents some measurements for determining thermal conductivity in different materials, using a single thermistor. This thermal conductivity measurement technique is appropriate for materials like fine-grained soils, gel-like materials such as silicon grease, and insulation materials. To verify the usefulness of this method, additional measurements are needed for several materials with well-known thermal conductivities, especially solid materials with thermal conductivity in the range of 0.5-2.5 W/m C.

The current heat use refers normally to the average heat use in a country or a sector during the course of a year. But it is also important to be aware of the distribution of high to low use when estimating the potential for reducing total heat use.Energy statistical data published in the annual report from Statistics Sweden have been supplemented by a deeper analysis of distribution of heat use and systematic causes regarding high heat use.The aim of this paper is to explain the variation in heat use with respect to construction year, degree days and energy efficiency measures.In the Swedish energy efficiency debate, many voices refer to systematic causes for high heat use. However, the results from this study do not support this opinion, since the use distribution mostly comes from individual causes. The most important implication of the study results is that systematic policy measures will have a low impact on the total national energy efficiency.